Numerous agents and methods of fire fighting are known and can be selected for a particular fire, depending upon factors such as its size, location and the type of combustible materials involved. Halogenated hydrocarbon fire fighting agents have traditionally been utilized in the fire protection industry, in applications including fire prevention applications, which leave a breathable atmosphere in an enclosed area, total flooding applications, wherein an enclosure is completely filled (“flooded”) with an effective amount of the agent (e.g., computer rooms, storage vaults, telecommunications switching gear rooms, libraries, document archives, petroleum pipeline pumping stations, and the like), or in streaming applications wherein the agent is directed towards the location of the fire (e.g., commercial hand-held extinguishers). Such extinguishing agents are not only effective but, unlike water, also function as “clean extinguishing agents”, causing little, if any, damage to the enclosure or its contents.
The most commonly-used halogenated hydrocarbon extinguishing agents have been the bromine-containing compounds bromotrifluoromethane (CF3Br, Halon1301) and bromochlorodifluoromethane (CF2CIBr, Halon1211). These bromine-containing halocarbons are highly effective in extinguishing fires and can be dispensed either from portable streaming equipment or from an automatic total flooding system activated either manually or by some method of fire detection. However, due to the presence of Br and Cl atoms within their molecular structure these compounds have been linked to the destruction of stratospheric ozone (“ozone depletion”). The Montreal Protocol and its attendant amendments have mandated that Halon1211 and 1301 production be discontinued. Thus, there is a need in this field for substitutes or replacements for the commonly-used, bromine-containing fire extinguishing agents. Such substitutes should have a low ozone depletion potential (ODP); should have the ability to efficiently extinguish, control, and prevent fires, e.g., Class A (trash, wood, or paper), Class B (flammable liquids or greases), and/or Class C (energized electrical equipment) fires; and should be “clean extinguishing agents”, i.e., be electrically non-conducting, volatile or gaseous, and leave no residue following their use. Preferably, substitutes will also be low in toxicity, not form flammable mixtures in air, and have acceptable thermal and chemical stability for use in extinguishing applications. In addition, suitable Halon replacements should exhibit a minimum impact on climate change, i.e., they should not contribute significantly to global warming, being characterized by a low global warming potential (GWP).
Various different fluorinated hydrocarbons have been suggested for use as fire fighting agents, as described by M. L. Robin, “Halogenated Fire Suppression Agents”, in Halon Replacements: Technology and Science, A. W. Miziolek and W. Tsang, eds., ACS Symposium Series 611, American Chemical Society, Washington, D.C., August 1994, Chapter 9. For example, hydrobromofluorocarbons (HBFCs) and hydrochlorofluoro-carbons (HCFCs) have been proposed as substitutes for the Halon agents. Although effective as fire extinguishing agents, and characterized by lower ODPs compared to the Halons, HBFCs and HCFCs still contribute to the destruction of stratospheric ozone, and as a result their use and production has been slated for phase out.
In U.S. Pat. No. 5,117,917 the use of perfluorocarbons (PFCs), for example perfluoro-n-butane, as fire extinguishing agents is disclosed. The PFCs are efficient fire extinguishing agents agents and do not contribute to the destruction of stratospheric ozone (i.e., their ODP is equal to zero). However, the extremely high chemical and thermal stability of the PFCs results in their being characterized by very long atmospheric lifetimes. As a result of their long atmospheric lifetimes and their ability to absorb infrared (IR) radiation, the PFCs strongly contribute to global warming, and are characterized by very high GWPs.
In U.S. Pat. No. 5,759,430 the use of bromine-containing olefins as fire extinguishing agents is disclosed. While some bromine-containing olefins, for example 2-bromo-3,3,3-trifluoropropene (CF3CBr═CH2) have been disclosed to exhibit fire extinguishing characteristics, others, for example bromotrifluoroethylene (CF2═CFBr) have been reported to be flammable (Bromotrifluoroethylene MSDS, Air Liquide). The bromine-containing olefins are characterized by short atmospheric lifetimes and low GWP, but are also characterized by small, but non-zero ODPs. In addition, the relatively high toxicity of the bromo-olefins severely limits their applications.
In U.S. Pat. No. 5,124,053 the use of hydrofluorocarbons (HFCs) as fire extinguishing agents is disclosed. The HFCs are characterized by efficient fire suppression, zero ODP, low toxicity, and are also “clean” agents, leaving no residues following their use. The HFCs are, however, characterized by moderate GWPs and hence contribute somewhat to global warming.
In U.S. Pat. No. 6,478,979 the use of perfluorinated ketones as fire extinguishing agents is disclosed. These compounds are characterized by efficient fire suppression, zero ODP and low GWP. However, the perfluorinated ketones are also characterized by high chemical reactivity (cf. N. P. Gambarayan, et. al., Angew. Chemie Intern. Ed., 5(11), 947 (1966); A. M. Lovelace, et. al., Aliphatic Fluorine Compounds, ACS Monograph Series, 1958, p. 180.). For example, the ketone CF3CF2C(O)CF(CF3)2 reacts with water to form the highly acidic, highlytoxic, and corrosive perfluoroacid perfluoropropionic acid, CF3CF2COOH, this hydrolysis reaction also occurring when the compound is absorbed across the lung/air interface.